Plan item H.2. Also fixes a real bug shipped in 0.2.35.

THE BUG: load_quantized_dit was imported from longcat_video.modules.longcat_video_dit,
where it does not exist — it is in longcat_video.modules.quantization (beside
QuantizedLinear and quantize_model), and it returns the AVATAR transformer, consistent
with INT8 being an avatar-1.5-only build. The wrong import would have raised at the exact
moment someone asked for INT8.

TRAINING. coderai does not implement this loop, and the reasons are the design:

1. LongCat's venv is standalone (Python 3.10 / torch 2.6 / transformers 4.41), so a
   trainer there cannot `from codai.api import loras` the way tools/lora_train_worker.py
   does — that overlay venv inherits the parent's site-packages, this one does not.
2. The upstream repo has NO way to create trainable LoRA layers. Its DiT exposes
   load_lora() / enable_loras() / disable_all_loras() and nothing that initialises one,
   and th...